The process of glucuronide formation leads to the formation of hydrophilic metabolites which are readily excreted by the kidney and liver. This serves as an important regulatory mechanism for the termination of drug and endobiotic action and as a detoxification mechanism in the case of xenobiotic exposure. Enzymes catalyzing glucuronidation have been shown to be products of a supergene family; these are termed UDP- glucuronosyltransferases (UGTs). The objectives of this application are to continue studies directed at an understanding of the structure and function of UGTs which catalyze the glucuronidation of morphine, other opioid agonists or antagonists and non-opioid tertiary amines, such as, antidepressants, antihistamines and antipsychotics whose metabolism leads to the major quaternary ammonium glucuronide excretory products in humans. In addition, studies are proposed to explore the function of a UGT that is abundant in human liver which catalyzes aromatic carcinogenic amine glucuronidation. mRNA for a steroid reactive UGT human liver (UGT2B15) has been discovered in brain. Since this protein catalyzes estrogen catechol glucuronidation and since estrogen catechols present in brain have important biological functions, such as hormonal release from the pituitary, studies have been designed to characterize the brain regions which might be involved in the UGT2B15-mediated glucuronidation of steroid hormones such as the estrogens and their catechol derivatives. Since morphine glucuronidation has been shown in human brain, UGTs involved in human brain metabolism of morphine will also be studied. Techniques involving molecular cloning and expression of cDNAs in human embryonic kidney (HK)293 cells will be used as the isolated relevant UGT cDNAs are isolated. Specific oligonucleotide and antibody probes will be available to assist in accomplishing the aims and objectives proposed in the application. Over 200 substances including drugs, steroids, simple phenols, monoterphenoids, bulky aliphatic alcohols, flavonoids, coumarins, and bilirubin will be tested as substrates for UGT cDNA encoded protein products. The observation that many UGTs, including those isolated in this laboratory, react with many natural plant-derived products often present in the diet as well as drugs and endobiotics indicates that the research proposed in this application will provide information, not only on potential drug-drug interaction, but on possible drug-natural product interaction.